1. Twenty-four healthy black Kenyan children, mean age 29 (SD 19) months, were studied over a 24 h period. Energy expenditure (EE) was determined using a ventilated-hood indirect calorimeter; measuring oxygen consumption and carbon dioxide production. Metabolizable energy intake was measured in twenty children. Anthropometric measurements were used to estimate surface area and lean body-weight.

2. The mean daily intake of metabolizable energy was 338.4 (se 28.4) kJ/kg; 70% of gross dietary energy being provided by carbohydrate. The level of postprandial EE was significantly (P > 0.05) higher than the resting level (12.6 (se 0.47) and 11.38 (se 0.37) kJ/kg per h respectively) while the level of the postprandial respiratory quotient (RQ) was similar to the resting level (0.94 (se 0.02)) and 0.98 (se 0.03 respectively). In 33% of total observations of the resting RQ the value was more than 1.0. These findings suggest that short-term fat storage may be a normal feature of metabolism in children, and also that the energy cost of (postprandial) fat synthesis is increased by a high-carbohydrate diet.

3. Values for the resting metabolic rate and various estimators of body size were compared using regression analysis. It was evident that, in these young children with considerable variation in body composition, body-weight remained a satisfactory metabolic-size estimator.

1. The effects of protein-deficient and energy-deficient diets on the concentrations of skin glycosaminoglycans (GAGs) and collagen were studied in young rats.

2. In Expt 1, comparisons were made between animals fed on a control (C) diet (protein:energy (P:E) 0.210), a low-protein (LP) diet (P:E 0.032) and a very-low-protein (VLP) diet (P:E 0005) ad lib. Skin GAGS and collagen concentrations were determined at intervals as the animals became malnourished and when some of those fed on the VLP diet started showing signs of oedema. Concurrently, plasma albumin concentrations were determined to assess the extent of hypoalbuminaemia. With prolonged severe protein deficiency all GAGS species were reduced below normal levels. Collagen concentration decreased with prolonged protein deficiency. Protein-deficient rats developed hypoalbuminaemia.

3. In Expt 2, comparisons were made between animals fed on the C, LP and VLP diets ad lib. and others given the C diet in restricted amounts sufficient to maintain body-weights identical to those fed on LP or VLP diets ad lib. Energy-deficient rats, wasting at rates similar to protein-deficient ones, had higher skin GAGs concentrations than those in protein-deficient or control animals. With prolonged malnutrition, collagen concentrations were similar in protein- and energy-deficient animals and lower than those observed in control animals. Plasma albumin concentrations in energy-deficient animals were above starting values, except in severely energy-deficient animals at the end of the experiment. Protein-deficient animals developed hypoalbuminaemia.

4. In conclusion, the present study has shown that the main difference between prolonged severe protein deficiency and energy deficiency in the rat is that skin hyaluronic acid concentration is higher than normal in energy deficiency but below normal levels in prolonged severe protein deficiency. Initially skin collagen concentrations are higher than normal in both protein- and energy-deficient animals. However, with prolonged malnutrition the concentrations are reduced.

1. Twelve young men were given for periods of 20 d, each of three mixed diets, namely a low-protein (LP) diet (9% total energy as protein, 67% of animal origin), a high-animal-protein (HA) diet (16% total energy as protein, 67% of animal origin) and a high-vegetable-protein (HV) diet (16% total energy as protein, 67% of vegetable origin). Retention of calcium, magnesium, iron, zinc and copper as well as various bowel function indices were investigated during each dietary period.

2. Neither the HA diet nor the HV diet changed the retention of the minerals considerably. Only Fe balance decreased significantly on the HV diet.

3. Substituting the HV diet for the HA diet resulted in significant increases in faecal wet weight (17 g/d), defaecation frequency (0.12 stools/d), faecal volatile fatty acids (2.6 mmol/d) and a decrease in faecal bile acids (128 μmol/d).

4. It is concluded that a HV diet, rather than a HA diet is to be recommended with respect to bowel function, whereas the HV diet does not necessarily have a significant influence on mineral retention.

1. To evaluate the effect of age, sex and level of intake on the colonic response to wheat fibre, thirty healthy volunteers aged 17–62 years (nineteen men, eleven women) recruited from a local industry, were divided into four groups and given a controlled diet for two 3-week periods. The diet contained white bread during one period or one of four different amounts of bran-enriched wholemeal bread during the other (30, 60, 110, 170 g/d).

2. Wide variation was observed between subjects in stool weight on the basal diet and in response to wheat fibre. Stepwise regression analysis showed that the variation in stool weight was significantly related to sex (t4.0, P <0.001) but not to age, height, weight or energy:fibre intakes on the basal diet. Stool weight in men (162(SE 11) g/d) was approximately double that in women (83(SE 11) g/d). Transit time and stool weight were closely related and the effect of sex on stool weight could be explained entirely by differences in transit.

4. Faecal carbohydrate excretion increased with the addition of bran mainly due to increased amounts of cellulose and pentose (arabinose+xylose), whilst digestibility of dietary non-starch polysaccharide fell from 77.6 (SE 2.3)% on the white bread diet to 65.6 (SE 2.4)% with the added bran (t 7.4, P < 0.01, n26).

5. Faecal pH was more acid in men than in women and was related to methane production. Methane producers had higher faecal pH than non-producers (7.06 (SE 0.1 1) v. 6.65 (SE O.1)), lower stool weight (g/d; 93 (SE 12) v. 156 (SE 13)) and slower transit times (h; 84.6 (SE 11.7) v. 48.6 (SE 6.6)).

6. These studies show that, when on similar diets, women have much lower stool weights and slower transit times than men. Furthermore, within the range of amounts of wheat fibre used in this and other published work, stool weight increases in linear proportion to the dose of fibre added to the diet. Methane excretion in breath is associated in this group of subjects with slow transit time and high faecal pH.

1. In vitro activation of erythrocyte aspartate aminotransferase (EC 2.6.1.1) activity by pyridoxal phosphate was used to assess vitamin B4 nutritional status in forty Sudanese women taking combined, low-dose oral contraceptives (oestrogen-progestogen; OC) and in thirty healthy, non-pregnant women not taking OC.

2. Fourteen (35%) out of forty OC users showed apparent vitamin B4 deficiency.

3. Side-effects associated with OC were more common among the apparently vitamin-B4-deficient OC users than among OC users and non-OC users not deficient in vitamin B4.

1. Four experiments, each with four concurrent continuous cultures of rumen micro-organisms, were used to investigate the effects of inoculum, food substrate and cobalt supplementation on the course of fermentation and vitamin B12 synthesis. The inocula came from sheep receiving either a Co-rich, complete diet (Ruminant A: Expts 1, 2 and 4) or a Co-deficient hay (Expt 3). In Expt 2, inocula from different donors were used for each culture but for other experiments they were pooled. Co-deficient hay was used as the initial substrate and Co-supplements were given after 8–54 d Co-depletion.

2. In three of four experiments, two using a pooled inoculum, uncharacteristically low acetate (Ac) and high propionate (Pr) outputs were obtained from the hay substrate in some cultures. In all, six cultures gave Ac:Pr values in the effluent > 2: 1 and, in Expt 3, the differences remained evident for at least 6 d after a change to a Co-deficient barley substrate.

3. Abnormal cultures gave lower cobalamin (cbl) and vitamin B12 analogue outputs than normal cultures: when supplemented with Co they showed small responses in cbl and large responses in analogue output with a slow increase in Ac:Pr.

4. We suggest that the use of Co-deficient substrates led to shifts in the microbial populations of some cultures, indicating the cbl-dependence of some species of rumen micro-organisms.

1. Sheep were given 800 g low-protein roughage/d at 2 h intervals and infused intraruminally with 0, 500, 750, 1000, 1250, 1500 or 2000 mmol sodium chloride/d in 436 ml water. The digestibility of various food fractions and rumen ammonia, volatile fatty acids (VFA) and liquid turnover rate were measured, along with renal haemodynamics and the renal excretory patterns of nitrogen and electrolytes. Ad lib. food intake was determined during the infusion of 0 and 2000 mmol NaCl/d.

2. Infusion of NaCl up to 750 mmol/d had virtually no effect on the indices measured, except water intake and water excretion. Infusion of greater amounts caused a step-wise decrease in the digestibility of organic matter (OM) and N. Rumen liquid turnover rate was increased substantially and rumen NH2, and VFA concentrations were decreased. Ad lib. food intake was not different when either 0 or 2000 mmol NaCl/d were infused into the rumen.

3. The glomerular filtration rate and effective renal plasma flow (ERPF) were substantially increased after the infusion of 1250 mmol or more NaCl/d. Extracellular fluid volume was also increased. The renal excretion of urea and uric acid+allantoin (URAL) were decreased at the higher infusion rates but the fractional excretions of both these substances were enhanced. The excretion of sodium, chloride, calcium and magnesium were markedly increased with increasing salt infusion.

4. The results suggest that high NaCl inputs into the rumen increase the rumen turnover rate, which in turn decreases the digestibility of OM, particularly N. This causes lower rumen NH3, and VFA concentrations. Plasma urea and URAL concentrations are also decreased and this causes lower renal excretion of these substances despite a much higher fractional excretion resulting from the greatly enhanced urine flow rate.

5. When roughages low in N are given, NaCl intake should be kept below 20 mmol/kg body-weight per d to prevent a decline in the digestibility of the food and any consequent reduction in protein available to the sheep.

1. Sulphur amino acid metabolism in livers from rats which had been fed ad lib. on a restricted diet (malnourished) or a Zn-deficient diet was investigated. Perfusion of normal livers with different amounts of L-methionine revealed that homocysteine was recycled four to five times before being eliminated via the transsulphuration pathway.

2. From the perfusion experiments, we found no evidence that any of the enzymes involved in recycling homocysteine back to methionine (methylation pathway) were adversely effected by Zn deficiency or malnutrition.

3. The intracellular concentration of cystathionine and S-adenosylmethionine increased in all livers in response to increased concentrations of L-methionine (L-Met) in the perfusate.

4. The intracellular concentration of S-adenosylhomocysteine remained the same in all livers regardless of the concentration of perfusate methionine.

5. Although homocysteine did not accumulate in the cell, it was excreted into the perfusate. The amount of homocysteine in the perfusate of livers from Zn-deficient rats was higher than either ad lib. or pair-fed rats.

6. The breakdown of homocysteine, via the transsulphuration pathway, was augmented by Zn deficiency. This was apparent from the greater amount of α-ketobutyrate excreted by livers from Zn-deficient rats compared with pair-fed or ad lib.-fed controls.

7. The increase in metabolism of L-Met, via the transsulphuration pathway, in the livers from Zn-deficient rats appears to reflect the lack of demand for this compound in protein synthesis and methylation reactions (Wallwork & Duerre, 1985).

1. The effect of protozoa on digestion in the rumen was studied using either defaunated or faunated sheep.

2. Six wethers, each fitted with rumen and simple duodenal cannulas, were given two isonitrogenous diets containing either lucerne (Medicago sativa) hay (diet L) or sodium hydroxide-treated wheat straw (diet S). The diets were given in eight equal portions per day at 3-h intervals. The mean intake of dry matter, 53 g/kg body-weight0.75 per d, was similar for the two diets and each diet had a similar digestible organic matter content. Diet L promoted a large protozoal population and was rich in nitrogen sources of low rumen-degradability, while diet S supported a smaller protozoal population and was rich in rumen-degradable N.

3. Digesta flow at the duodenum was estimated by means of a dual-marker technique using chromium-mordanted lucerne hay and polyethylene glycol as markers. The microbial flow at the duodenum was estimated using diaminopimelic acid (DAPA), nucleic-acid purine bases (PB) and 35S incorporation simultaneously. The different microbial markers were compared in the defaunated sheep. Protozoal N contribution was estimated in faunated sheep.

4. Defaunated sheep had lower rumen ammonia concentrations and molar proportions of butyric acid than faunated sheep, but they had higher molar proportions of propionic acid.

5. Rumen organic matter digestion was reduced by defaunation, but this decrease was compensated for by increased intestinal digestion.

6. There was a net increase of N flow (approximately 10 g/d) between mouth and duodenum in defaunated sheep. This was explained by increases in both microbial and dietary N flows from the rumen compared with faunated sheep.

7. The influence of protozoa on solid- and liquid-phase retention times in the rumen is discussed, as well as the protozoal contribution to microbial N flow in the duodenum of faunated sheep.

1. Duplicate groups of rainbow trout (Salmo gairdneri) were each given partially purified diets which were either adequate or depleted in selenium for 40 weeks.

2. Although there was no significant difference in weight gain, liver Se concentration was significantly lower in fish given the deficient diet.

3. Glutathione (GSH) peroxidase (EC 1. 11. 1. 9) activity was significantly reduced in liver of Se-deficient fish but a differential assay did not indicate the presence of a non-Se-dependent GSH peroxidase activity, although liver GSH S-transferase (EC 2. 5. 1. 18) was significantly increased.

4. Perfusion of livers from trout given Se-adequate diets with t-butyl hydroperoxide (BuOOH) or hydrogen peroxide caused an increase in the rate of release of glutathione disulphide (GSSG) into the perfusate.

5. Perfusion of livers from Se-deficient trout with BuOOH or H2O2 did not result in any change in rate of release of GSSG into the perfusate.

6. These findings confirm the absence of any compensatory non-Se-dependent peroxidase activity in Se-depleted trout.

1. Pure swards of perennial ryegrass (Lolium perenne L. cv. Melle) or white clover (Trifolium repens L. cv. Blanca) were harvested daily as either primary growth (May-June) or mid- (July) and late- (August-September) season 4-week regrowths and offered to Friesian steers at two levels of feed allowance (18 and 24 g dry matter (DM)/kg live weight), to examine the effect of forage species and stage of harvest on nutrient digestion and supply.

2. The early- and mid-season grasses had low nitrogen (23 g/kg DM) and high water-soluble carbohydrate (169 g/kg) contents whilst the late-season grass had a higher N content (28 g/kg). All clover diets had high N (average 45 g/kg) and low water-soluble carbohydrate (89 g/kg) contents, and DM digestibility on all diets ranged from 0.77 to 0.83 (mean of two feeding levels).

3. Mean total rumen volatile fatty acid concentrations were significantly (P < 0.001) higher on the clover diets, whilst on the grass diets molar proportions of propionate showed a slight but not significant decline with advancing season and tended to be higher than those on the clover diets. Mean rumen ammonia concentrations were significantly (P < 0.001) lower on the early- and mid-season grasses (59 mg NH3-N/1) than the late-season grass (242 mg/l) and early-season clover (283 mg/l) which were all significantly (P < 0.01) lower than the mid-and late-season clovers (372 and 590 mg/l) respectively.

4. Rates of organic matter (OM) and N digestion in the rumen were estimated using established nylon-bag techniques and found to be high on all diets, but significant effects due to forage species (clover > grass; P < 0.001) were detected, whilst overall potential degradability in the rumen exceeded 0.89 for both OM and N on all diets.

5. Significantly (P < 0.001) more OM entered the small intestine of calves fed on white clover (10.2 g/kg live weight) than those fed on ryegrass (8.33 g/kg) and similar effects due to level of feeding (g/kg; low 7.9, high 10.6; P < 0.05) and stage of harvest (g/kg; early 8.3 v. mid 10.0, late 9.50; P < 0.05) were also detected. Non-NH3-N (NAN) flow (g/kg) to the small intestine was increased by forage species (grass 0.56, clover 0.69; P < 0.05) and stage of harvest (early 0.59 v. mid 0.65, late 0.64; P > 0.05) whilst NAN flow/N intake ranged from 0.96 to 1.65 g/g (mean 1.25) on the grass diets and from 0.64 to 0.84 g/g (mean 0.75) on the clovers (P < 0001).

6. Microbial N flow to the small intestine averaged 0.72 of duodenal NAN (grass 0.76, clover 0.69). Efficiency of microbial N synthesis was high on all diets, (g/kg OM truly digested in the rumen; grass 33.5, clover 36.3), as was the estimated extent of in vivo feed N degradation (g/g N intake; grass 0.75, clover 0.79).

7. A model is described to simulate the progress curves of the ratio, degraded N:degraded OM in the rumen for the six diets, using indices obtained in the present study. The results are ratified with the in vivo observations of N utilization in the rumen for the grass and clover diets.

8. It is concluded that both forage species and stage of harvest can significantly influence the processes of rumen digestion and nutrient supply, but with the fresh forages examined in the present study, it would appear that the processes of digestion in the rumen greatly outweighed the passage of potentially digestible nutrients from the rumen.

1. The dynamics of large ciliate (holotrich) protozoa (Isotricha and Dasytricha spp.) in the rumen of cattle given cut, fresh ryegrass (Lolium multiflorium Lam) were studied by means of a single intrarumen injection of 14C-labelled protozoa prepared in vitro by adding [Me 14C]choline to rurnen fluid containing protozoa and incubating at 39° for 2 h.

2. An indication of the lysis rate of protozoa in the rumen was obtained from the radioactivity apparently lost through the methane pool.

3. The turnover time of the holotrich protozoa indicates that these protozoa were extensively retained in the rumen and that only a small proportion of those produced in the rumen flowed out in the digesta. This was supported by the estimation of the rate of lysis which was approximately 85% of the turnover rate in the rurnen.

4. The apparent production rate of the larger protozoa indicates that they contribute only about 9% of the predicted net microbial protein synthesis in the rumen.

1. The characteristics of digestion, passage and rumen fill of three hays: early- and late-cut perennial ryegrass (Loliurn perenne cv. Endura) and white clover hay (Trifolium repens cv. Blanca and Pronitro) were studied using six rumen-cannulated sheep fed at a restricted level of intake (18 g dry matter (DM)/kg live weight (LW) per d), in a two 3 x 3 Latin square design.

2. Voluntary intake of the same diets was measured using a further six non-cannulated sheep in a similar design.

3. Rate of digestion of the three hays was measured using dacron bags and the rates of digestion of DM and neutral-detergent fibre (NDF) for clover hay were significantly (P < 0.05 and P < 0.001 respectively) faster than those for the two grass hays whose rates did not differ. Rates of passage, determined using chromium-mordanted hay, did not differ between treatments.

4. Rumen pool sizes of DM, organic matter and fibre were generally greatest for the late-cut grass hay and lowest for the clover hay, while voluntary intake was highest (P < 0.001) for the clover hay (36.6 g DM/kg LW per d) and lowest for the late-cut grass hay (24.7 g/kg LW per d).

5. The net rate of removal of indigestible fibre from the rumen appeared to vary within the day, with maximal disappearance occurring during eating, followed by a lag phase between 5 and 10 h after feeding, with a second increase in rate between 10 and 24 h post-feeding.

1. Eight wether sheep were offered a diet of perennial ryeigrass (Litum perenne cv. Endura) hay once daily at two levels of intake (11 and 16.5 g dry matter (DM)/kg live weight (LW)) with or without maize starch (175 g DM/kg hay DM). The experiment consisted of four periods. each lasting 32 d. Rates of digestion of the hay were measured by incubation in dacron bags and rates of passagc using chromium-mordanted hay. Rumen pool sizes of DM, organic matter and fibre were measured by emptying the rumen.

2. The inclusion of starch in the diet appeared to increase significantly (P < 0.01) the lag phase before the start of fibre digestion, as observed both in the dacron bag studies and in the slower initial disappearance of digestible neutral-detergent fibre (NDF) from the rumen recorded by emptying of rumen contents. However, there was no significant effect of starch on apparent digestibility of fibre in the whole tract.

3. The main effect of increasing the level of feeding wax, to increase the rate of passage with a consequent decrease in overall digestibility. The fractional rate of passage increased from 0.0318 to 0.0400 as the level of feeding increased, while apparent digestibility of NDF decreased from 0.755 to 0.724.

4. On all treatments the weight of indigestible fibre in the rumen remained more or less constant between 5, 10 and 15 h after feeding, but was significantly lower at 24 h. These results suggest that a high proportion of the outflow of material from the rumen not associated with feeding appears to occur during the second half of the feeding cycle.

1. Expt 1. Six 200 kg Hereford heifers fitted with rumen and abomasal cannulas were fed adlib. on alkali-treated oat straw sprayed with urea and minerals, with no supplement (O), or 700 g rolled barley (B) or cottonseed meal (C)/d, in a 3 x 3 Latin square with two replicates.

2. Intakes of the basal diet were not significantly affected by the supplements. Intakes of digestible organic matter (OM) were 3135, 3325 and 3515 g/d on diets O, Bland C respectively. Abomasal OM flow on diet C was 13 and 12% higher than on diets O and B respectively (P < 0.05) which was associated with a decrease in the proportion of OM intake apparently digested in the rumen ( P < 0.05) and an increase in the proportion of abomasal OM digested in the lower gut ( P < 0.05).

3. Total nitrogen and bacterial N flows at the abomasum were significantly higher (P < 0.01 and P < 0.05 respectively) on diet C than on diets O and B. Efficiency of bacterial N synthesis on diet C was 19 and 28% higher than on diets 0 and B respectively ( P < 0.05).

4. Dry matter (DM) pool size in the rumen was greater on diet C than on diets O and B (P < 0.05).

5. Expt 2. Thirty-three 210 kg Friesian heifers were allocated to the same treatments as in Expt I. Intakes of the basal straw diet were not significantly affected by the supplements. Intakes of digestible OM were 3.80, 4.16 and 4.34 kg/d on diets O, B and C respectively.

6. Rumen ammonia and plasma urea levels were significantly higher on diet C than on diets O and B ( P < 0.05).

7. Live-weight gains were 679, 838 and 1051 g/d on diets O, B and C respectively ( P < 0.01) and live-weight gain/MJ metabolizable energy intake was highest on diet C (P < 0.01).

8. It was concluded that the growth response to barley was attributable to the increase in energy supply, and that the additional response to cottonseed meal was attributable to greater protein absorption arising from greater abomasal flows of bacterial and dietary proteins.

1. The significance of blood urea-nitrogen transfer to the rumen was examined in sheep given alkali-treated wheat straw supplemented with 3.5 (diet A), 5.9 (diet B) and 11.6 (diet C) g urea-N/kg dry matter (DM).

2. Mean voluntary intakes of DM (g/d) were 897, 1149 and 1225 for diets A, B and C respectively, indicating significant (P < 0.05) intake responses to urea supplementation. Digestion studies were conducted at 90% of voluntary intake. Dietary N intakes (g/d) were 7.1, 11.5 and 18.6 for diets A, B and C respectively.

3. Absorption of ammonia-N from the rumen (g/d) was 3.5, 6.7 and 8.9 for diets A, B and C respectively, with all dietary differences being significantly different (P < 0.05).

4. Non-ammonia-N (NAN) leaving the abomasum (g/d) was 9.6, 12.7 and 14.8 for diets A, B and C respectively. Microbial N leaving the abomdsum (g/d) was 6.8, 9.6 and 10.7 for diets A, B and C respectively. Hence, significantly (P < 0.05) more N was provided to the intestines with increased urea supplementation. Net efficiencies of microbial protein synthesis (g N/kg organic matter apparently digested in the rumen), estimated from 16N incorporation, were 24.2, 23.7 and 25.3 for diets A, B and C respectively, and were not significantly different (P > 0.05).

5. Calculated proportions of microbial N derived from rumen NH2-N were 1.05, 0.95 and 0.91 for diets A, B and C respectively, reflecting the high proportion of total N as urea-N in the diets. Proportions of microbial N derived from blood urea-N were 0.31, 0.21 and 0.12 for diets A, B and C respectively, indicating a decreasing significance of blood urea as a source of microbial N as dietary urea increased (P < 0.05).

6. Transfer of blood urea-N to the rumen (g/d) was 3.8, 4.7 and 2.6 for diets A, B and C respectively, being significantly (P < 0.05) lower on diet C. Using an estimate, of the salivary contribution of urea-N to the rumen, it was concluded that there was a significant though not large transfer of blood urea-N across the rumen wall on all diets.

7. Net transfer of blood urea-N to the rumen was estimated from a two-pool model and was +0.4 g/d for diet A, though this was not significantly different from zero. Net transfers for diets B and C were -2.0 and - 6.3 g N/d respectively.

8. Significant intake responses to exogenous urea supplementation were observed because of a limited capacity to recycle N to the rumen under the conditions of low dietary N supply imposed.

1. The effects of dietary polychlorinated biphenyls (PCB) and excess tyrosine on serum and liver lipids, urinary ascorbic acid and catecholamines were compared in male Wistar rats.

2. Serum levels of cholesterol, urinary ascorbic acid, norepinephrine, epinephrine, dopamine and histamine were significantly increased in rats given either PCB or excess tyrosine.

3. The hypercholesterolaemia induced by PCB or excess tyrosine was blocked by the adrenergic α-blocker, phenoxybenzamine.

4. The present results suggest causal interrelations between the hypercholesterolaemia induced by dietary PCB or excess tyrosine and the secretion of catecholamines.